Avalanche Forecast

Issued: Mar 19th, 2019 4:00PM

The alpine rating is high, the treeline rating is high, and the below treeline rating is high. Known problems include Loose Wet, Persistent Slabs and Deep Persistent Slabs.

lisa paulson, Parks Canada

Little Yoho.

http://www.pc.gc.ca/apps/scond/Cond_E.asp?oID=34810&oPark=100092 The avalanche cycle continues. With the on-going blast of heat, calm winds and clear sky conditions, expect the danger to climb to HIGH with daytime heating.

Summary

Weather Forecast

Clear skies again tonight will help freeze the snowpack despite the relatively warm overnight temperatures. Conditions will deteriorate rapidly with another clear and calm day for Wednesday where temperatures at treeline will climb to 10-15C. This diurnal spring like pattern will continue until the weekend.

Snowpack Summary

Sun crusts or moist snow on solar aspects and moist snow at lower elevations. 10-20 cm of recent snow sits over a mix of facets, sun crust and wind slabs above treeline, and over 30-50 cm of weak facets elsewhere. While a supportive mid-pack exists in thicker areas, weak facets to the ground are seen in many thin areas.

Avalanche Summary

A widespread spring avalanche cycle continues with the bulk occurring on solar aspects as they heat up through the day. Avalanche size ranged from size 1-3. Most slides have been within the surface snow (March 7 interface) with some stepping down a bit deeper; however, we have seen only a few avalanche step down to the basal layers.

Confidence

The weather pattern is stable

Problems

Loose Wet

Rapidly warming daytime temperatures and high solar inputs are causing loose wet avalanches to start by mid morning. Some of these are running long distances or triggering slabs along the way. Avoid exposure to these slopes when they heat up.

Use extra caution on slopes if the snow is moist or wet.If triggered the loose wet sluffs may step down to deeper layers resulting in large avalanches.

Aspects: East, South East, South, South West, West.

Elevations: All elevations.

Likelihood

Very Likely - Certain

Expected Size

1 - 3

Persistent Slabs

10-20 cm settled snow (since Mar 7) has formed slabs above treeline due to winds and warm temperatures. They sit over a variety of weaker surfaces. Natural and skier triggering of this recent snow has occurred in the last several days on all aspects.

Use conservative route selection, stick to moderate angled terrain with low consequence.Watch for surface cracking and stiffer surface layers of snow.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1 - 3

Deep Persistent Slabs

We are starting to see places where avalanches are failing on the basal weaknesses and scrubbing to ground. This is mostly occurring with large triggers in thin rocky areas but we expect this type of avalanche activity to increase with more heat.

Be aware of the potential for full depth avalanches due to deeply buried weak layers.Pay attention to overhead hazards like cornices which could easily trigger deep slabs.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 3.5

Valid until: Mar 20th, 2019 4:00PM